1. Field of the Invention
The invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing the same.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write head having an induction-type electromagnetic transducer for writing and a read head having a magnetoresistive element (hereinafter, also referred to as MR element) for reading.
The write head comprises: a bottom pole layer and a top pole layer including pole portions that are opposed to each other and placed in regions on a side of an air bearing surface; a write gap layer provided between the pole portion of the bottom pole layer and the pole portion of the top pole layer; and a thin-film coil arranged such that at least a part thereof is insulated from the bottom pole layer and the top pole layer.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a write head. To achieve this, it is required to implement a write head of a narrow track structure wherein the width of the pole portions of the bottom and top pole layers on a side of the air bearing surface, that is a write track width, is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
Additionally, in order to prevent an increase in effective write track width due to magnetic flux expansion in between the pole portion of the bottom pole layer and the pole portion of the top pole layer, there has conventionally been adopted a structure in which the pole portion of the top pole layer and at least a part of the pole portion of the bottom pole layer are given an equal width. This structure is referred to as a trim structure.
FIG. 21 is a perspective view showing an example of the structure in the vicinity of the pole portions of a write head. In this example, a write gap layer 109 is formed on a bottom pole layer 108. A thin-film coil that is not shown and an insulating layer 112 for covering the thin-film coil are formed on the write gap layer 109. An end of the insulating layer 112 closer to an air bearing surface 130 is located at a predetermined distance from the air bearing surface 130, thereby defining a throat height. The throat height is the length (height) of portions of two pole layers facing each other with the write gap layer in between, as taken from the end closer to the air bearing surface 130 to the other end. A top pole layer 113 is formed on the write gap layer 109 and the insulating layer 112.
The top pole layer 113 has: a first portion 113A that includes the pole portion; and a second portion 113B that includes a yoke portion. The width of the first portion 113A is constant and equal to the write track width. The width of the second portion 113B is equal to the width of the first portion 113A at the interface with the first portion 113A. It gradually grows wider as the distance from the air bearing surface 130 increases, and then becomes constant.
A part of the first portion 113A is laid on the write gap layer 109, the part extending from the end of the first portion 113A located in the air bearing surface 130 to a position corresponding to the end of the insulating layer 112 closer to the air bearing surface 130. The other part of the first portion 113A is laid on the insulating layer 112. The second portion 113B is mostly laid on the insulating layer 112. The second portion 113B, at a part near its end farther from the air bearing surface 130, is connected to the bottom pole layer 108 through a contact pole formed in the write gap layer 109.
In a region where the first portion 113A of the top pole layer 113 and the bottom pole layer 108 are opposed to each other with the write gap layer 109 in between, a trim structure is formed, that is a structure in which the first portion 113A, the write gap layer 109, and a part of the bottom pole layer 108 closer to the write gap layer 109 have an equal width.
The trim structure as shown in FIG. 21 is formed, for example, by the following steps. That is, the second portion 113B of the top pole layer 113 is initially covered partially with an etching mask made of a photoresist, from a position halfway through its spreading part to the side farther from the air bearing surface 130. Next, the write gap layer 109 and a part of the bottom pole layer 108 closer to the write gap layer 109 are etched by dry etching. Here, the first portion 113A of the top pole layer 113 not covered with the etching mask is used as a mask. For example, reactive ion etching is used for etching the write gap layer 109; ion beam etching (ion milling) is used for etching the bottom pole layer 108.
In the thin-film magnetic head shown in FIG. 21, the first portion 113A of the top pole layer 113 has a constant thickness.
Now, if the width of the first portion 113A of the top pole layer 113, that is, the write track width, falls to 1 xcexcm or below, for example, the magnetic flux may be saturated halfway through the first portion 113A, possibly precluding the efficient use of magnetomotive force generated by the thin-film coil for writing.
To avoid this, the first portion 113A of the top pole layer 113 can be increased in thickness. Hard disk drives, however, have some skew between the direction perpendicular to the surfaces of the bottom and top pole layers 108, 113 and the track direction. This results in a problem that the increased thickness of the first portion 113A of the top pole layer 113 can cause so-called side write, which means that data is written in regions of a recording medium where data is not supposed to be written, and so-called side erase, which means that data is erased from regions where data is not supposed to be written.
An object of the present invention is to provide a thin-film magnetic head and a method of manufacturing the same, capable of preventing magnetic flux saturation in the middle of the magnetic path and preventing data from being written/erased in regions where data is not supposed to be written, even at smaller track widths.
A thin-film magnetic head according to the present invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. Here, the second magnetic layer has a first portion and a second portion. The first portion has an end located in the medium facing surface, has a constant width equal to a write track width, and includes the pole portion. The second portion is coupled to the other end of the first portion and includes a yoke portion, The thickness of the first portion in a region extending from the end of the first portion located in the medium facing surface to a predetermined position is smaller than the thickness of the other part of the second magnetic layer adjacent to that region.
A method of manufacturing a thin-film magnetic head according to the present invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The method comprises the steps of:
forming the first magnetic layer;
forming the gap layer on the first magnetic layer;
forming the second magnetic layer on the gap layer; and
forming the thin-film coil such that the at least part thereof is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. Here, the second magnetic layer is formed to have a first portion and a second portion. The first portion has an end located in the medium facing surface, has a constant width equal to a write track width, and includes the pole portion. The second portion is coupled to the other end of the first portion and includes a yoke portion. The thickness of the first portion in a region extending from the end of the first portion located in the medium facing surface to a predetermined position is made smaller than the thickness of the other part of the second magnetic layer adjacent to that region.
In the thin-film magnetic head or the method of manufacturing the same according to the present invention, the thickness of the first portion in the above-mentioned region is smaller than the thickness of the other part of the second magnetic layer adjacent to that region. This makes it possible to reduce the thickness of the first portion in the medium facing surface while preventing magnetic flux saturation halfway through the magnetic path of the second magnetic layer.
In the thin-film magnetic head or the method of manufacturing the same according to the present invention, the thickness of the first portion in the above-mentioned region may fall within a range of 30% to 95% the thickness of the other part of the second magnetic layer adjacent to that region.
In the thin-film magnetic head or the method of manufacturing the same according to the present invention, the predetermined position may be located within a range that extends from a position 0.5 xcexcm away from the end of the first portion located in the medium facing surface to the interface between the first and second portions.
In the thin-film magnetic head or the method of manufacturing the same according to the present invention, the predetermined position may be located within a range that extends from a position at a distance of one seventh the length of the first portion from the end of the first portion located in the medium facing surface to the interface between the first and second portions.
In the thin-film magnetic head or the method of manufacturing the same according to the present invention, at least a part of the pole portion of the first magnetic layer closer to the gap layer may have a width equal to the width of the first portion.
In the method of manufacturing a thin-film magnetic head according to the present invention, a layer to be the second magnetic layer may be partially etched so that the thickness of the first portion in the above-mentioned region is made smaller than the thickness of the other part of the second magnetic layer adjacent to that region. Here, the etching may be effected by dry etching using an etching mask, or by local etching using no etching mask.
The method of manufacturing a thin-film magnetic head according to the present invention may further comprise a trimming step in which at least a part of the pole portion of the first magnetic layer closer to the gap layer is etched using at least a part of the first portion adjacent to the medium facing surface as a mask, so that at least a part of the pole portion of the first magnetic layer closer to the gap layer has a width equal to the width of the first portion.
In the method of manufacturing a thin-film magnetic head according to the present invention, in the trimming step a layer to be the second magnetic layer may be partially etched concurrently, so that the thickness of the first portion in the above-mentioned region is made smaller than the thickness of the other part of the second magnetic layer adjacent to that region. Here, the etching may be effected by dry etching using an etching mask.
In the method of manufacturing a thin-film magnetic head according to the present invention, the layer to be the second magnetic layer may be partially etched after the trimming step, so that the thickness of the first portion in the above-mentioned region is made smaller than the thickness of the other part of the second magnetic layer adjacent to that region. Here, both the etching in the trimming step and the etching of the layer to be the second magnetic layer may be effected by dry etching using an etching mask. Alternatively, the etching in the trimming step may be effected by dry etching using an etching mask while the etching of the layer to be the second magnetic layer may be effected by local etching using no etching mask.
The other objects, features, and advantages of the present invention will become fully apparent from the following description.